Hardwood floors are extremely popular for a wide variety of sporting activities and residential purposes. Hardwood floors provide an aesthetically appealing floor surface of stable and consistent construction.
Some types of wood floors or wood floor systems comprise a plurality of elongated floor strips laid end-to-end in parallel rows. Other types of wood floors, including those referred to as “parquet” floors, vary in layout somewhat from only parallel rows of floor strips. These other types of floor layouts may have various sections with floorboards arranged in longitudinal and transverse directions relative to a given space, or even arranged diagonally, or at another angle. Nevertheless, even with these other types of floor layouts, there are usually at least some portions of the floor wherein a plurality of end-to-end floor strips or boards reside in parallel rows.
This invention relates generally to wood floors wherein the entire floor or a portion of a floor has a plurality of floor strips laid end-to-end in parallel rows, but this invention is particularly advantageous for those floors wherein the entire floor comprises parallel rows of floorboards arranged along one direction.
Floors of this type typically have a tongue and groove construction to reinforce the individual floorboards and to facilitate stable securement of the floorboards to an underlying surface at the same desired vertical level. Once installed, the tongues and grooves along the longitudinal side surfaces of the floorboards help to stabilize the floor system so that no single floorboard or row of floorboards is able to move vertically relative to the rest of the floor. Typically, the elongated tongue and groove construction of such floorboards is cut into the side surfaces of the floorboards by a saw, and this is done by the floorboard manufacturer at the same time the top and bottom surfaces of the individual floorboards are formed. Parallel rows of floorboards are usually secured to an underlying subfloor or base, one row at a time, as the installer works his way across the floor.
It is well known among hardwood floor manufacturers and installers that wood building products, particularly elongated wood floorboards or floor strips, undergo expansion and contraction due to moisture ontake and egress, which result from humidity changes in the surrounding environment. With respect to a plurality of rows of parallel floorboards, almost all of this expansion and contraction occurs laterally, or transverse, to the longitudinal direction of the floorboards. There are even some hardwood floor systems, particularly those suited for athletic use, wherein the subfloor structure is specifically designed to permit lateral movement of the floorboards due to transverse expansion and contraction relative to an underlying base. U.S. Pat. No. 4,856,250 discloses such a floor.
Because of these expansion and contraction forces, installers of hardwood floors are required to place spacers between every few rows of floorboards. For example, washers having a width of about {fraction (3/16)}″ every five, six or seven rows of a typical basketball floor comprising parallel rows of maple floor strips. This use of spacers in installing parallel rows of floorboards for a hardwood floor has been practiced for quite a long time. This practice is so well accepted that it is usually required in bid specifications or installation instructions for floors of this type. Typical spacers used by a floor installer are coin-like in shape, of uniform thickness, and they are placed between an already installed row of floorboards and the next layer of floorboards which is to be installed. The spacers limit or dictate the horizontal space between these two rows of floorboards. With a plurality of spacers of uniform width, this spacing should be uniform along the length of the two floorboard rows. Once the second row of floorboards has been installed at the desired spacing from the first row of floorboards, the spacers are removed. This leaves a spacer slot or seam of predetermined dimension.
This use of spacers in the hardwood floor industry represents an attempt to provide some degree of control over expansion and contraction of the floorboards, by providing some open space for lateral floorboard expansion every few rows of the floor. If such voids or spaces were not provided, expansion of tightly engaged parallel rows of floorboards due to humidity would invariably result in buckling of the floor at its weakest point. Stated another way, the spacers provide desired open spaces between every few rows of floorboards, thereby significantly reducing the occurrence of buckling of the floor. It is generally recognized in the hardwood floor industry that spacers of this type are necessary for proper installation of a hardwood floor, if it is desired to minimize the potential for buckling of the floor and to assure that the floor will have a long life.
However, the use of spacers in installing a hardwood floor system also creates a number of problems. For one thing, the need to locate the spacers between two rows of floorboards for every few rows of the floor, and then to subsequently remove the spacers represents a labor cost for the floor installer. Also, even though a floor installed with spacers is less susceptible to buckling than a typical floor installed without any spacers, those portions of the floor which reside between the spacer seams still have some potential for buckling even though there is little or no possibility for buckling along the spacer seam. In other words, the buckling potential for the floor is not uniform as one moves transversely across the rows of the floorboards.
To understand a number of additional disadvantages with the use of spacers, it is necessary to understand some common practices associated with installing and finishing a typical hardwood floor. Usually, after the floor has been secured to an underlying subsurface, the floor is first sanded and then it is finished with a liquid finishing solution. Currently, most liquid finishing solutions are oil based, but water based liquid finishes are becoming more popular, and are even required by law in some states due to environmental concerns. As an alternative to installing a floor and then sanding and finishing the already-installed floor at the use site, the floor may be prefinished at the manufacturing site and then shipped to the use site. When a floor is prefinished, it is temporarily laid out over a base, but it is not permanently fastened thereto. Thereafter, it is sanded, finished and then packaged for shipment to the installation site. Spacers are not necessary when the floor is temporarily laid out for refinishing at the manufacturer's site, but the spacers are typically used during permanent installation at the use site.
When the liquid finishing solution is applied to a floor, the liquid solution tends to migrate downwardly along the side surfaces of the rows of floorboards. This is true for prefinishing at the site of manufacturer or finishing at the use site. However, for the spacers for a floor finished at the installation site, the spacer seams are particularly susceptible to this situation. In fact, with such rows the downward liquid solution flow can more accurately be characterized as a waterfall rather than a migration of liquid solution.
When a water based finishing solution of this type moves downwardly between the side surfaces of parallel rows of floorboards, and perhaps even to the bottom surfaces of the floorboards, it eventually dries and adhesively bonds together the surfaces it is sandwiched between. This bonding effect has even been characterized as being similar to applying a “superglue” between the bonded surfaces. This bonding effect along the side surfaces of the floorboard rows tends to make the floor respond to expansion and contraction more like a monolithic structure than a plurality of parallel rows of floorboards, at least for some portions of the floor. In some instances, this bonding may result in preventing the floor from expanding into the voids created by the spacer seams. This is particularly true if the water based finished solution has migrated all the way to the bottom surfaces of the floorboards. As a result of the adhesive bonding caused by the water based finish, the floor can effectively become almost like a plurality of parallel monolithic floor portions separated by the spacer seams. When this occurs, subsequent significant contraction of the floorboards may cause the spacer seams to widen to the point where the floorboard tongues of these seams can be seen from above.
Although an oil based finishing solution does not usually have the same adhesive bonding effect of a water based finished solution, it also represents other disadvantages. For one thing, the oil based finish takes quite a significantly longer time to dry, and therefore may continue to reside along the side surfaces or even the bottom surfaces of the floorboards for some time after installation. Thereafter, any significant lateral expansion of the floorboards could cause the oil based finish to creep upwardly along the seams and onto the upper surface of the floor, resulting in an unsightly and potentially dangerous floor surface. Applicants are aware of at least one actual installed floor where this situation has occurred. Thus, the application of a liquid finish to a hardwood floor, i.e., whether water based or liquid based, has been known to generate problems with the long-term stability and/or appearance of the floor, particularly along spacer seams of the floor.
Another problem with installation of floors of this type is called “overwood.” This term and situation refers to the amount of floorboard material which extends above a floorboard in an adjacent row. This may result from undesired expansion of the floorboards during prefinishing, or even some mismatching of the vertical levels of the tongue and groove of adjacently located floorboards. This may occur because it is common to precisely machine, or cut, the top surfaces of the floorboards, to assure the best fit on the top surface, but not necessarily the bottom and side surfaces. These side surfaces usually have lower tolerances. It is an object of the invention to reduce the time and costs associated with installing a hardwood floor which includes at least some parallel rows of elongated floorboards.
It is another object of the invention to more evenly distribute the lateral expansion and contraction forces to which a typical hardwood floor of this type is subjected, due to humidity changes.
It is still another object of the invention to eliminate the downward migration of finishing solution between side-by-side floorboard rows of a hardwood floor, and the serious problems associated therewith.
It is still another object of the invention to reduce the costs associated with applying a liquid finish to a hardwood floor.
It is still another object of the invention to minimize the amount of overwood between adjacent rows of floorboards of a wood floor.